feat: company names for tickers (Alpaca backfill + subtle display)

Store an optional company name on Ticker (migration 014) and backfill it from
Alpaca's asset list in a single Trading-API call for the whole universe — no
per-ticker fetch. Runs automatically at the end of universe bootstrap and via a
manual "Backfill Names" button (admin) / POST /admin/tickers/backfill-names.

The name ships on /tickers; a shared symbol→name map (useTickerNames) lets any view
show it without its own request. Displayed subtly next to the symbol — in the global
search, the ticker header, and as a small muted line under the symbol in Top Setups
and Open Trades (no extra column, truncated so it never widens the table).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/models/ticker.py

@@ -11,6 +11,9 @@ class Ticker(Base):
 
     id: Mapped[int] = mapped_column(primary_key=True)
     symbol: Mapped[str] = mapped_column(String(10), unique=True, nullable=False)
+    # Company name (e.g. "Biogen Inc."); backfilled from Alpaca, nullable for
+    # symbols Alpaca doesn't know.
+    name: Mapped[str | None] = mapped_column(String(120), nullable=True)
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), default=datetime.utcnow, nullable=False
     )